Hi,
Go to OLMB - Define Attributes of System Messages - Settings for System Messages and set the message M7 092 as Error message as shown below:
Also, ensure that the material status 20 (in your case) is with IM as error message B as shown below in OMS4:
Now, system will throw error message once you try to post / try to count the PI for the material. Test the scenario and revert back.
Regards,
AKPT